1. Field of the Disclosure
The present disclosure relates to obtaining signals in a swept-wavelength system used in oil exploration and production.
2. Description of the Related Art
In various aspects of oil exploration and production, optical sensors are deployed downhole and a light source at a surface location supplies a measurement light beam to the optical sensors over a fiber optic cable. Upon interaction with the optical sensors, the measurement beam is sampled at the surface location to obtain measurements using a synchronized trigger signal obtained from a suitable light beam (trigger beam). In swept-wavelength interferometry systems, in which the light source is swept across a range of wavelengths, synchronization can be difficult. Since the optical path length for the returned light (typically 10 kilometers or more in oil exploration and production) is much greater than the optical path of the trigger beam (typically a few meters), the measurement beam returning to the surface location is often delayed with respect to the trigger beam, resulting in a loss of synchronization. Current methods for compensating for the differences in optical path length require introducing fiber optic cable and/or optical switches into the path of the trigger beam. These methods are often cumbersome and space-consuming and can produce signal loss. The present disclosure provides a method and apparatus for obtaining a measurement from a sensor using an intrinsic delay of the fiber optic cable.